We counted 1000 cells using oil immersion microscopy (x 1000).

We did not use ApopTag.

See attached paper.

As far as I know TUNEL assay is based on fluorescent microscopy, you could quantitate the fluorescent microscopy images by logismics as Image J. Here is the paper that a same technique was used for ROS quantitation 10.1016/j.bcp.2020.113900

During our early work on apoptosis, the monolayer cells were floated in collected medium on trypsinization, and cytospinned on clean slide. They were stained with PI or Hoechst 33258, then 500 cells were counted and the proportions of popcorn-like cells with fragmented nuclei were calculated. Mean values from different tests were counted. When the microscopic figures were presented in a conference poster on CSH Symposium, a question was raised from the audience: how did you collect so many cells? Actually some people only stained the cells grown on slides.